Adaptive impedance matching networks are known in the field of electrical and electronic engineering. Such networks may make use of distributed actuation and detection to simplify a control algorithm of the adaptive matching network.
A problem associated with such impedance matching networks is that the impedance matching range may be limited. For example, an impedance matching network may comprise a variable LC-network having a matching range limited by the tuning range of the variable elements (capacitors and/or inductors) and the frequencies of operation.
FIG. 1 is a block diagram of a conventional GSM/UMTS front-end including an adaptive antenna matching network and adaptive load-line. A number of disadvantages are associated with such an arrangement. Impedance tuning range limitation, especially for multi-band operation, is a particular problem.
In other words, the limited tuning range of variable capacitors, and inductors, limits the impedance matching range of a variable network. Further, the range of impedance matching of a variable network is frequency dependent.
Although the Con/Coff ratio of radio-frequency micro-electromechanical systems (RF-MEMS) devices is relatively large, an enhanced matching range still remains desirable because impedance mismatch between electronic devices (i.e., antenna mismatch) can be extreme. In case of load-line adaptation, a large impedance tuning range is desirable because output power levels vary over wide ranges. Additional tuning range may also be required in case of multi-band applications.